1. Technical Field
The present disclosure relates to a sewing machine including a holder which holds a workpiece cloth to be sewn and a transfer mechanism to which the holder is detachably attachable and which transfers the holder holding the workpiece cloth on a sewing machine bed freely in a predetermined direction, the sewing machine being capable of executing an embroidery sewing operation.
2. Related Art
There has conventionally been provided a multineedle embroidery sewing machine which can continuously execute embroidery sewing with the use of multicolor embroidery threads, for example. The multineedle embroidery sewing machine is provided with a needle bar case which is mounted on a distal end of an arm and has, for example, six needle bars. A predetermined one of the needle bars is selectively coupled to a needle bar driving mechanism thereby to be vertically driven. A control device of the sewing machine controls a multicolor embroidery sewing operation, based on pattern data which orders a needle position per stitch, that is, an amount of movement of workpiece cloth, color change and the like. In the embroidery sewing operation, the needle bar driving mechanism and other driving mechanisms are controlled while an embroidery frame holding the workpiece cloth is moved in the X and Y directions by the transfer mechanism.
The above-described multineedle embroidery sewing machine includes a type that can embellish workpiece cloth by a needle punch or punch needle embroidery technique. In this type of sewing machine, punch needles are attached to some of the needle bars instead of sewing needles so that a needle punch is applied to the workpiece cloth based on needle punch information.
An apparatus has recently been provided which engraves desired photograph, illustration, characters and the like on the surfaces of a plastic or metallic plate and a board made of wood or fabric using striking needles, thereby producing accessories and furnishing goods. An apparatus automatically executing the engraving includes an engraving apparatus to which a dot impact printer is applied. In this engraving apparatus, a workpiece is moved in the Y direction while a printer head provided with a plurality of striking needles is moved in the X direction, whereby a predetermined engraving is applied to the surface of the workpiece.
The inventors conceived use of the aforementioned multineedle embroidery sewing machine as an apparatus for performing the above-described engraving by attaching one or more striking needles to embroidery sewing needles, instead of the embroidery sewing needles. In this case, a holder which fixedly holds a workpiece is mounted to a carriage of the transfer mechanism, instead of an embroidery frame holding the workpiece cloth. A needle bar to which the a striking needle is attached is moved up and down while the workpiece is moved by the transfer mechanism based on engraving data, whereby a predetermined pattern or the like is considered to be engraved on the surface of workpiece cloth.
However, when a striking needle is attached to the needle bar and an engraving operation is executed by moving the needle bar upward and downward as described above, there is a possibility that the user may erroneously bring something into contact with the stamping needle in operation thereby to interrupt the stamping operation.
Furthermore, one turn of a main shaft moves the stamping needle upward and downward once. Accordingly, the number of striking operations has a one-to-one relation with the number of revolutions of the main shaft. The following problem occurs when a striking speed or working efficiency is to be increased. When the main shaft is rotated at 500 rpm, for example, the striking operation is carried out at 500 times per minute. In this case, the rotational speed of the main shaft needs to be doubled into 1000 rpm in order that the striking speed may be doubled, whereupon a time period of high speed rotation of the sewing machine is prolonged. This reduces endurance times or service lives of the needle bar driving mechanism and components such as the sewing machine motor driving the needle bar driving mechanism.